A new procedure was presented with the objective of proving that it is the generalization of current attempts in designing compressed members and structures which is able to solve cases where other authors have problems. It is the further development of the former methods published by Chladný, Baláž, Agüero et al., which are based on the shape of the elastic critical buckling mode of the structure. Chladný’s method was accepted by CEN/TC 250 working groups creating Eurocodes. Both current Eurocodes EN 1993-1-1:2005 and EN 1999-1-1:2007 in their clauses 5.3.2(11) enable applying the geometrical equivalent unique global and local initial (UGLI) imperfection. The imperfection has the shape of the elastic critical buckling mode with amplitude defined in 5.3.2(11). UGLI imperfection is an alternative to the global sway and local bow initial imperfections defined in 5.3.2(3) and to the imperfections described in the clause 5.3.2(6). The determination of the location and value of UGLI imperfection proved to be onerous by some authors, especially in cases of members with variable cross-sections or/and axial forces. The paper also provides for special cases a procedure to detect the critical cross-section along the member which is defined as the one in which the utilization factor obtains maximum values. The new approach is validated by the investigation of five complex structures made of steel and one made of aluminum alloy solved by other authors. Comparisons of the results with those of other authors and with the Geometrically and Materially Nonlinear Analysis with Imperfections (GMNIA) results showed very good agreements with negligible differences. The information concerning the differences between current Eurocodes EN 1993-1-1:2005 and EN 1999-1-1:2007 is provided. Working drafts of Eurocodes of new generation prEN 1993-1-1:2020 and prEN 1999-1-1:2020 are also commented on.

This part analyzed GFRP rebar’s research situation, summarized its behaviuor as internal reinforcement for concrete structures. The research has been developed over recent years, however the rules and standard codes for design RC concrete structures with these rebars not consider that the internal reinforcement can work in compression. This paper presents the development of the research to get a new kind GFRP rebar for work as internal reinforcement of concrete structures, with an innovative design for work both in tension and compression, and their mechanical properties: strength, bond,…

Let G be a graph with no isolated vertex and let $N\left(v\right)$ be the open neighbourhood of $v\in V\left(G\right)$. Let $f:V\left(G\right)\to \{0,1,2\}$ be a function and $V_i=\{v\in V\left(G\right):f\left(v\right)=i\}$ for every $i\in \{0,1,2\}$. We say that f is a strongly total Roman dominating function on G if the subgraph induced by $V_1\cup V_2$ has no isolated vertex and $N\left(v\right)\cap V_2\ne \varnothing$ for every $v\in V\left(G\right)\backslash V_2$. The strongly total Roman domination number of G, denoted by ${\gamma }_{tR}^s\left(G\right)$, is defined as the minimum weight $\omega \left(f\right)={\sum }_{x\in V\left(G\right)}f\left(x\right)$ among all strongly total Roman dominating functions f on G. This paper is devoted to the study of the strongly total Roman domination number of a graph and it is a contribution to the Special Issue “Theoretical Computer Science and Discrete Mathematics” of Symmetry. In particular, we show that the theory of strongly total Roman domination is an appropriate framework for investigating the total Roman domination number of lexicographic product graphs. We also obtain tight bounds on this parameter and provide closed formulas for some product graphs. Finally and as a consequence of the study, we prove that the problem of computing ${\gamma }_{tR}^s\left(G\right)$ is NP-hard.

Fire engineering endeavours to mitigate injury or the loss of life in the event of a fire. This is achieved primarily through fire prevention, containment, and extinguishment measures. Should prevention fail, the structural integrity of buildings, coupled with effective evacuation strategies, becomes paramount. While glass fibre-reinforced polymer (GFRP) materials have demonstrated efficacy in reinforcing concrete elements, their performance under fire conditions, notably in comparison to steel, necessitates a deeper understanding for structural applications. This study experimentally and numerically investigates the fire performance of GFRP-reinforced concrete (RC) columns subjected to only fire load without additional external loads. The research aims to ascertain the fire resistance based on the thickness of the concrete coating and the ultimate tensile strength of GFRP rebars after 90 min of fire exposure. Four GFRP-RC columns were subjected to a standardized fire curve on all sides in the experimental program. In the analytical program, a theoretical model was developed using the heat transfer module of the COMSOL software. The results of both analyses were very close, indicating the reliability of the procedure used. Based on the findings, recommendations regarding the fire resistance of GFRP-RC columns were formulated for structural applications. Results from this research provide the civil engineering community with data that will help them continue using FRP materials as internal reinforcement for concrete.

This article investigates the structural resistance of thin-walled steel sections classified as Classes 1 to 4 under Eurocode 3. The study focuses on flexural capacity, and takes into consideration the effects of local buckling and the bimoment. Although Class 1 and 2 sections can develop complete plastic resistance, Class 3 sections are limited to elastic behavior prior to local instability. For Class 4 sections, effective width methods are employed to account for the reduction in strength due to early local buckling. Based on Eurocode formulations, these approaches are extended to incorporate the influence of the bimoment, which is significant in thin-walled open sections under non-uniform torsion. A comparative analysis between analytical models and numerical simulations is presented, with an emphasis on how the bimoment alters stress distributions and reduces the effective widths of slender plates. The results underscore the necessity of including these effects in the structural design of thin-walled members, particularly for open profiles subjected to bending and warping.